Method of making printing head for thermal printer

ABSTRACT

A plurality of heating resistors and their lead wires are formed upon a heat-resistive flexible film, and the flexible film is then curved and mounted upon a head structure in such a manner that the heating resistors are arrayed along a projecting edge of the head structure.

United States Patent [1 1 Hiruma et a1.

METHOD OF MAKING PRINTING HEAD FOR THERMAL PRINTER Inventors: Kenji Hiruma; Inawo Sugaya, both of Tokyo, Japan Assignee: Ricoh Co. Ltd., Tokyo, Japan Filed: Aug. 14, 1972 Appl. No.: 280,091

Related US. Application Data Division of Ser. No. 178,876, Sept. 9, 1971, Pat. No. 3,715,564.

Foreign Application Priority Data Sept. 16, 1970 Japan 45/81085 US. Cl. 29/611 Int. Cl. 1105b 3/00 Field of Search 29/611, 610;

156/583; 40/28 R; 93/D1G. 1; 219/216, 243, 543, 549; 346/76 R Jan. 1, 1974 [56] References Cited 7 UNITED STATES PATENTS 2,802,086 8/1957 Fener 219/536 X 3,161,457 12/1964 Schroeder et a1 346/76 R 3,327,314 6/1967 Zeuthen 3,578,946 5/1971 Colello 346/76 R Primary ExaminerRichard J. Herbst Assistant Examiner-V A. Dipalma Att0rneyHenry T. Burke et a1.

[57] ABSTRACT A plurality of heating resistors and their lead wires are formed upon a heat-resistive flexible film, and the flexible film is then curved and mounted upon a head structure in such a manner that the heating resistors are arrayed along a projecting edge of the head structure.

5 Claims, 5 Drawing Figures I PAIENIEDJAN new m 1 [IF 2 METHOD OF MAKING PRINTING I-IEAD FOR THERMAL PRINTER This is a division of application Ser. No. 178,876, filed Sept. 9, l97l, and now United States Pat. No. 3,715,564.

BACKGROUND OF THE INVENTION This invention relates to printing heads for so-called thermal printers, and to methods of manufacturing such heads.

A typical thermal printer includes a printing head which comprises a matrix of heating resistors. Printing is effected by exposing a heat-sensitive recording paper or the like to the head while passing electric current through selected ones of the aforementioned resistors so as to form on the paper a mosaic pattern or image of the heated resistors, e.g., a pattern constituting a letter, numeral or other symbol. Thermal printing heads of the type described are commonly formed by various known micro-electronic techniques. Although thermal printers may advantageously be used (for-example) asiprinters of electronic computers, they have the drawback that these known processes for manufacture of printing heads are undesirably complex and costly.

SUMMARY OF THE INVENTION An object of the invention is to provide an improved printing head for thermal printers which can overcome the above-described disadvantages, and a method of manufacturing the same.

To this and other ends, the present invention broadly contemplates the provision of a printing head for thermal printers wherein a plurality of heating resistors and their lead wires are formed upon a heat-resistive film and the heat-resistive film is then curved at the heating resistors and mounted upon a head structure.

The invention further contemplates the provision of a method for manufacture of printing heads for thermal printers comprising the steps of forming upon a heatresistive film a plurality of heating resistors and their lead wires as by vacuum evaporation or photoetching, curving or bowing the film, and mounting the heatresistive film upon a head structure in such a manner that the heating resistors are disposed along a projecting portion of the head structure.

I BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a printing head embodying the present invention in a particular form;

FIG. 2 is a top view of the head of FIG. 1, illustrating the position of the printing head relative to a heatsensitive recording paper;

FIG. 3 is a view illustrating how a numeral (three) is formed and recorded by the printing head of FIGS. 1 and 2;

FIG. 4 illustrates the pulse current wave forms to be applied to the printing head to form and record the numeral three as shown in FIG. 3; and

FIG. 5 is a view for explanation of the manufacture of printing head films used in the printing head shown in FIG. 1.

DETAILED DESCRIPTION In a printing head for a thermal printer in accordance with thepresent invention as illustrated in FIG. 1, a plurality of thin-film heating resistors 2 and thin-film conductors 3 (which serve as lead wires) are formed upon a surface of a heat-resistive and electrically nonconductive flexible film support 1 made from (for example) fluoroplastics, with the resistors disposed in a straight row (i.e., in spaced relation to each other along a straight line) on the film support surface. The support 1 is bowed or curved at an appropriate radius of curvature, with the row of resistors 2 disposed along the vertex of the bend or curve, and is securely fixed to a head structure 4 made from (for example) a heat-resistive plastic. The thin-film conductors 3 are individually coupled to separate flexible cables 6 at their connections 5. The head structure 4 is tapered at 7, defining a projecting rectilinear edge along which the outwardly facing resistors 2 are arrayed, in order to ensure satisfactory contact between the thin-film resistors 2 and a heat-sensitive paper, and is carried by a shaft 8 which is coupled to a driving mechanism (not shown).

The relative position of the writing head with respect to the heat-sensitive recording paper is best shown in FIG. 2. That is, the heat-sensitive recording paper 9 is placed in close contact with the thin-film resistors 2.

As stated, and as best shown in FIG. 1, the seven thinfilm resistors 2 are arrayed in a straight row for simultaneous engagement with the surface of the recording paper 9, and are displaced successively along the surface of the paper in five steps in the direction (perpendicular to the row) indicated by the arrow in FIG. 2. Therefore, a letter or numeral which is formed of a combination of (7 X 5) elementary mosaic areas may be printed upon the recording paper 9 as for example shown in FIG. 3.

In FIG. 3, a numeral three printed in the manner described above is illustrated. The letters L, L

designate the seven thin-film heating resistors 2, and the letters T, T designate the number of steps. The pulse wave forms applied to the thin-film heating resistors 2 to print this numeral three (3) are shown in FIG. 4. That is, the pulse current is applied to the thin-film resistors 2,, 2 2,, and 2 at the time or step T, so that these thin-film resistors dissipate heat to change the color of the elementary areas L,, L L, and L, in the,

column T,. At the time T the pulse currents are applied to the thin-film resistors 2, and 2-, so that the color of the elementary mosaic areas L, and L, in the column T are changed by heat. In like manner, the pulse currents shown in FIG. 4 are applied to the indicated selected thin-film resistors 2 at T T and T so that the selected elementary mosaic areas change their colors. Thus the numeral three is printed as shown in FIG. 3. It is seen that any letter or numeral may be formed by applying the pulse currents to the selected thin-film resistors 2 as they are displaced.

Next referring to FIG. 5, the method for manufacture of the printing head described hereinabove in reference to FIG. 1 will be described. The thin-film heating resistors 2 are formed in a straight row or column upon the heat-resistive flexible film support 1 by vacuum evaporation ofa nickel-chromium alloy or photo etching. In the similar manner the thin-film conductors 3 are formed for example by vacuum evaporation of gold. In FIG. 5 only a limited number of thin-film resistors and conductors 2 and 3 are shown for clarity, but it is to be understood that any desired number of film resistors and conductors may be formed. Each printing head pattern (four patterns are shown in FIG. 5) is cut off, and bowed or curved with the thin-film resistors 2 disposed along the vertex of the curve or bend, and securely fixed to the head structure as described in reference to FIGS. 1 and 2.

The printing head for a thermal printer in accordance with the present invention is simple in construction and light in weight and is adapted for mass production because the thin-film resistors and conductors may be formed upon the heat-resistive film by vacuum evaporation or photoetching. Thus the printing head may be manufactured at less cost than heads formed by processes heretofore conventionally used.

In the embodiment described above, the thin-film resistors have been described as being arrayed in one row or column, but it is to be understood that various variations and modifications can be effected within the scope of the present invention. For example, a plurality of printing head structures may be stacked so as to form and record a letter or numeral without displacing in step the single printing head. In this case, the head structures 4 are not curved or tapered (as in the embodiment illustrated in FIG. 1), but are made thin with equal thickness and electrically insulated from each other. Furthermore, a plurality of printing heads capable of forming and recording a letter or numeral without shifting may be arrayed so that a plurality of letters or numerals may be formed and recorded simultaneously.

What is claimed is:

l. A method of manufacturing printing heads for a thermal printer comprising the steps of a. forming upon a heat-resistive flexible film support a plurality of heating resistors and a plurality of lead wires respectively connected to said resistors;

b. curving or bowing said flexible film support; and

c. mounting said flexible film support on a head structure in such a manner that only said heating resistors are projected along said head structure.

2. In a method of manufacturing a printing head for a thermal printing device, the steps of a. establishing a row of heating resistors and a plurality of leads respectively connected to said resistors on a surface of a flexible film member, and

b. mounting the flexible film member on a head structure having a projecting edge portion, the mounting step including bending the film member around said edge portion with said row of resistors exposed and coincident with the vertex of the bend so as to be positionable in simultaneous contact with a surface of a recording medium.

3. A method according to claim 2, wherein said heating resistors and said leads are thin metallic films adherent to the surface of said film member.

4. A method according to claim 3, wherein the step of establishing the resistors and leads on the film member surface comprises depositing thin metallic films on the surface by vacuum evaporation.

5. A method according to claim 3, wherein the step of establishing the resistors and leads on the film member surface comprises depositing thin metallic films on the surface by photoetching. 

1. A method of manufacturing printing heads for a thermal printer comprising the steps of a. forming upon a heat-resistive flexible film support a plurality of heating resistors and a plurality of lead wires respectively connected to said resistors; b. curving or bowing said flexible film support; and c. mounting said flexible film support on a head structure in such a manner that only said heating resistors are projected along said head structure.
 2. In a method of manufacturing a printing head for a thermal printing device, the steps of a. establishing a row of heating resistors and a plurality of leads respectively connected to said resistors on a surface of a flexible film member, and b. mounting the flexible film member on a head structure having a projecting edge portion, the mounting step including bending the film member around said edge portion with said row of resistors exposed and coincident with the vertex of the bend so as to be positionable in simultaneous contact with a surface of a recording medium.
 3. A method according to claim 2, wherein said heating resistors and said leads are thin metallic films adherent to the surface of said film member.
 4. A method according to claim 3, wherein the step of establishing the resistors and leads on the film member surface comprises depositing thin metallic films on the surface by vacuum evaporation.
 5. A method according to claim 3, wherein the step of establishing the resistors and leads on the film member surface comprises depositing thin metallic films on the surface by photoetching. 